Whey protein isolate conjugated with xylo-oligosaccharides via maillard reaction: Characterization, antioxidant capacity, and application for lycopene microencapsulation

In this study, lycopene was encapsulated in whey protein isolate-xylo-oligosaccharide conjugates prepared by Maillard reaction. The optimum preparation conditions were the weight ratio 1:2 of whey protein isolate to xylo-oligosaccharides, reaction temperature 90 °C, heating time 3 h and pH 9.0. The formation of the conjugate was confirmed by grafting degree and Fourier infrared spectroscopy. Glycosylation of whey protein isolate significantly enhanced the emulsification performance and antioxidant capacity. The encapsulation efficiency and encapsulation yield reached 94% and 86%, respectively. The solubility of lycopene microcapsules reached 92 g/L. Scanning electron microscopy images showed that lycopene microcapsules were spherical and the whole surface was continuous with some typical concavities. Moreover, glycosylated (whey protein isolate) exhibited a better protective effect on lycopene than (whey protein isolate) alone. Additionally, microcapsules based on glycosylated whey protein isolate significantly increased the bioaccessibility of lycopene from 16 ± 3% to 60 ± 4%. Therefore, whey protein isolate glycosylated with xylo-oligosaccharides by Maillard reaction can be used to encapsulate lycopene or other bioactives and improve their properties.